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Triethyl phosphonoacetate is a reagent for organic synthesis used in the Horner-Wadsworth-Emmons reaction (HWE) or the Horner-Emmons modification.
Triethyl phosphonoacetate can be added dropwise to sodium methoxide solution to prepare a phosphonate anion. It has an acidic proton that can easily be abstracted by a weak base. When used in an HWE reaction with a carbonyl the resulting alkene formed is usually the E alkene, and is generated with excellent regioselectivity. | 0 | Theoretical and Fundamental Chemistry |
A development of transition state theory in which the position of the dividing surface is varied so as to minimize the rate constant at a given temperature. | 0 | Theoretical and Fundamental Chemistry |
As mining techniques and the price of minerals improve, it is not unusual for tailings to be reprocessed using new methods, or more thoroughly with old methods, to recover additional minerals. Extensive tailings dumps of Kalgoorlie / Boulder in Western Australia were re-processed profitably in the 1990s by KalTails Mining.
A machine called the PET4K Processing Plant has been used in a variety of countries for the past 20 years to remediate contaminated tailings. | 1 | Applied and Interdisciplinary Chemistry |
There are currently three methods in use that involve precisely targeting a DNA sequence in order to introduce a double-stranded break. Once this occurs, the cell's repair mechanisms will attempt to repair this double stranded break, often through non-homologous end joining (NHEJ), which involves directly ligating the two cut ends together. This may be done imperfectly, therefore sometimes causing insertions or deletions of base pairs, which cause frameshift mutations. These mutations can render the gene in which they occur nonfunctional, thus creating a knockout of that gene. This process is more efficient than homologous recombination, and therefore can be more easily used to create biallelic knockouts. | 1 | Applied and Interdisciplinary Chemistry |
Rather than being immobilized within a gel matrix, DNA molecules were held in place by electrostatic interactions on a positively charged surface. Resolution improved such that fragments from ~30 kb to as small as 800 bp could sized. | 1 | Applied and Interdisciplinary Chemistry |
Ampicillin is one of the most used drugs in pregnancy, and has been found to be generally harmless both by the Food and Drug Administration in the U.S. (which classified it as category B) and the Therapeutic Goods Administration in Australia (which classified it as category A). It is the drug of choice for treating Listeria monocytogenes in pregnant women, either alone or combined with an aminoglycoside. Pregnancy increases the clearance of ampicillin by up to 50%, and a higher dose is thus needed to reach therapeutic levels.
Ampicillin crosses the placenta and remains in the amniotic fluid at 50–100% of the concentration in maternal plasma; this can lead to high concentrations of ampicillin in the newborn.
While lactating mothers secrete some ampicillin into their breast milk, the amount is minimal.
In newborns, ampicillin has a longer half-life and lower plasma protein binding. The clearance by the kidneys is lower, as kidney function has not fully developed. | 0 | Theoretical and Fundamental Chemistry |
Endogenous retroviruses are not formally included in this classification system, and are broadly classified into three classes, on the basis of relatedness to exogenous genera:
* Class I are most similar to the gammaretroviruses
* Class II are most similar to the betaretroviruses and alpharetroviruses
* Class III are most similar to the spumaviruses. | 1 | Applied and Interdisciplinary Chemistry |
A nipple is a short stub of pipe, usually male-threaded steel, brass, chlorinated polyvinyl chloride (CPVC), or copper (occasionally unthreaded copper), which connects two other fittings. A nipple with continuous uninterrupted threading is known as a close nipple. Nipples are commonly used with plumbing and hoses. | 1 | Applied and Interdisciplinary Chemistry |
The earliest surviving bimetallic strip was made by the eighteenth-century clockmaker John Harrison who is generally credited with its invention. He made it for his third marine chronometer (H3) of 1759 to compensate for temperature-induced changes in the balance spring. It should not be confused with the bimetallic mechanism for correcting for thermal expansion in his gridiron pendulum. His earliest examples had two individual metal strips joined by rivets but he also invented the later technique of directly fusing molten brass onto a steel substrate. A strip of this type was fitted to his last timekeeper, H5. Harrison's invention is recognized in the memorial to him in Westminster Abbey, England. | 1 | Applied and Interdisciplinary Chemistry |
Adatoms, due to having fewer bonds than the other atoms in the crystal, have unbound electrons. These electrons have spin and therefore a magnetic moment. This magnetic moment has no preference for orientation until an external influence, like a magnetic field, is present. The structure of the adatoms on a surface can be adjusted by changing the external magnetic field. Through this method theoretical situations, such as the atomic chain, can be simulated. Quantum mechanics needs to be taken into account when using adatoms due to the small scale.
The magnetic field created by an atom is caused mostly by the orbit and spin of the electrons. The protons and neutrons magnetic moment are negligible when compared to that of the electron due to their larger masses. When an atom with free electrons is inside an external magnetic field, its magnetic moment aligns with the external field because this lowers its energy. This is why bound electrons do not display this magnetic moment, they already have a favorable energy state and it is unfavorable to change. The magnetization of an (magnetically aligned) atom is given by:
Where N is the number of electrons, g is the g-factor, μ is the Bohr magneton, k is the Boltzmann constant, T is the temperature and j is the total angular momentum quantum number. This formula holds under the assumption that the magnetic energy of an electron is given by and there is no exchange interaction. | 0 | Theoretical and Fundamental Chemistry |
The apparatus consists of a gas chromatograph equipped with an odour port (ODP), in place of or in addition to conventional detectors, from with human assessors sniff the eluates. The odour port is characterised by its nose-cone design connected to the GC instrument by a transfer line. The odour port is commonly glass or polytetrafluoroethylene. It is generally placed 30–60 cm away from the instrument, extending from the side such that it is not affected by the hot GC oven. The deactivated silica transfer line is generally heated to prevent the condensation of less-volatile compounds. It is flexible so that the assessor can adjust it according to their comfortable sitting position. As traditional warm and dry carrier gases may dehydrate the mucous membrane of the nose, volatiles are delivered via auxiliary gas or humidified carrier gas, with relative humidity (RH) of 50–75%, to ease the dehydration.
The olfactometric detector may be coupled with, or connected in parallel to, a flame ionization detector (FID) or mass spectrometer (MS). Moreover, multiple odour ports may be set-up. In these cases, the eluate is generally split evenly between the detectors to allow it to reach the detectors simultaneously. | 0 | Theoretical and Fundamental Chemistry |
The physical presence of introns promotes cellular resistance to starvation via intron enhanced repression of ribosomal protein genes of nutrient-sensing pathways. | 1 | Applied and Interdisciplinary Chemistry |
Some [NiFe]-containing proteins are known to sense H and thus regulate transcription.
Copper-containing proteins are known to sense ethylene, which is known to be a hormone relevant to the ripening of fruit. This example illustrates the essential role of organometallic chemistry in nature, as few molecules outside of low-valent transition metal complexes reversibly bind alkenes. Cyclopropenes inhibit ripening by binding to the copper(I) center. Binding to copper is also implicated in the mammalian olfaction of olefins.
Carbon monoxide occurs naturally and is a transcription factor via its complex with a sensor protein based on ferrous porphyrins. | 0 | Theoretical and Fundamental Chemistry |
Iodobenzene dichloride (PhICl) is a complex of iodobenzene with chlorine. As a reagent for organic chemistry, it is used as an oxidant and chlorinating agent. | 0 | Theoretical and Fundamental Chemistry |
Vitamin D supplementation has been tentatively found to lead to a reduced risk of death in the elderly, but the effect has not been deemed pronounced, or certain enough, to make taking supplements recommendable. Other forms (vitamin D, alfacalcidol, and calcitriol) do not appear to have any beneficial effects with regard to the risk of death. High blood levels appear to be associated with a lower risk of death, but it is unclear if supplementation can result in this benefit. Both an excess and a deficiency in vitamin D appear to cause abnormal functioning and premature aging. The relationship between serum calcifediol concentrations and all-cause mortality is "U-shaped": mortality is elevated at high and low calcifediol levels, relative to moderate levels. Harm from vitamin D appears to occur at a lower vitamin D level in the black population than in the white population. | 1 | Applied and Interdisciplinary Chemistry |
Aluminium, like its congener boron, is less electronegative than carbon (Al, 1.61; C, 2.55); thus, aluminium-bound carbons in organoalanes possess partial negative charge and are nucleophilic as a result. Generally, however, organoalanes are not nucleophilic enough to transfer an organic group on their own (the exception being when carbonyl and enone acceptors are used, due to the high oxophilicity of aluminium). In most cases, nucleophilic activation of organoalanes is necessary for group transfer to take place. Like organoboranes, organoalanes possess an empty p orbital on the aluminium center that can receive electron density from an added nucleophile. The resulting negatively charged aluminate is much more nucleophilic than the neutral alane.
This concept has been applied to methods for the synthesis of organic compounds from alkenyl- and alkynylalanes. The most notable applications are methods for the stereospecific synthesis of olefins. Alkenylalanes, which are easily synthesized with complete stereocontrol through alkyne hydroalumination, transfer the alkenyl unit to a variety of electrophiles. Alkynylalanes are less commonly used because alkali metal acetylides can be used for many of the same transformations as alkynylalanes. However, alkynylalanes are useful for the coupling of tertiary halides and alkynes (a reaction difficult to effect with alkali metal alkynes) and for conjugate addition and epoxide opening reactions. | 0 | Theoretical and Fundamental Chemistry |
Hydroxyl tagging velocimetry (HTV) is a velocimetry method used in humid air flows. The
method is often used in high-speed combusting flows because the high velocity and temperature
accentuate its advantages over similar methods. HTV uses a laser (often an argon-fluoride
excimer laser operating at ~193 nm) to dissociate the water in the flow into H + OH. Before entering the flow optics are
used to create a grid of laser beams. The water in the flow is dissociated only where beams of
sufficient energy pass through the flow, thus creating a grid in the flow where the
concentrations of hydroxyl (OH) are higher than in the surrounding flow. Another laser beam (at either ~248 nm or ~308 nm) in
the form of a sheet is also passed through the flow in the same plane as the grid. This laser
beam is tuned to a wavelength that causes the hydroxyl molecules to fluoresce in the UV spectrum. The fluorescence is then captured by a charge-coupled device (CCD) camera. Using
electronic timing methods the picture of the grid can be captured at nearly the same instant
that the grid is created.
By delaying the pulse of the fluorescence laser and the camera shot, an image of the grid that
has now displaced downstream can be captured. Computer programs are then used to compare the
two images and determine the displacement of the grid. By dividing the displacement by the known
time delay the two dimensional velocity field (in the plane of the grid) can be determined. Flow ratios, however, are shown to affect the impingement locations, where increased air flow ratios can reduce the required combustor size by isolating reaction products solely within the secondary cavity.
Other molecular tagging velocimetry (MTV) methods have used ozone (O), excited oxygen and nitric oxide as the tag instead of hydroxyl. In the case of ozone the method is known as ozone tagging velocimetry or OTV. OTV has been developed and tested in many room air temperature applications with very accurate test results. OTV consists of an initial "write" step, where a 193-nm pulsed excimer laser creates ozone grid lines via oxygen (O) UV absorption, and a subsequent "read" step, where a 248-nm excimer laser photodissociates the formed O and fluoresces the vibrationally excited O product thus revealing the grid lines' displacement. | 1 | Applied and Interdisciplinary Chemistry |
Filiform corrosion may be considered as a type of crevice corrosion and is sometimes seen on metals coated with an organic coating (paint). Filiform corrosion is unusual in that it does not weaken or destroy the integrity of the metal but only affects the surface appearance. | 1 | Applied and Interdisciplinary Chemistry |
We can recognize which of these isometries we have according to whether it preserves hands or swaps them, and whether it has at least one fixed point or not, as shown in the following table (omitting the identity). | 0 | Theoretical and Fundamental Chemistry |
A drop from each solution (A and B) is dripped onto the substance being tested, causing the two solutions to mix together. | 0 | Theoretical and Fundamental Chemistry |
The family also contains L-lactate dehydrogenases that catalyse the conversion of pyruvate to L-lactate, the last step in anaerobic glycolysis. Malate dehydrogenases that catalyse the interconversion of malate to oxaloacetate and participate in the citric acid cycle, and L-2-hydroxyisocaproate dehydrogenases are also members of the family. The N-terminus is a Rossmann NAD-binding fold and the C-terminus is an unusual alpha+beta fold. | 1 | Applied and Interdisciplinary Chemistry |
Using matrix matched calibration standards can compensate for ion suppression. Using this technique, calibration standards are prepared in identical sample matrix to that used for analysis (e.g. plasma) by spiking a normal sample with known concentrations of analyte. This is not always possible for biological samples, since the analyte of interest is often endogenously present in a clinically significant, albeit normal, quantity. For matrix matched calibration standards to be effective in compensating for ion suppression, the sample matrix must be free of the analyte of interest. Additionally, it is important that there is little variation in test sample composition since both the test sample and the prepared calibration sample must be affected in the same way by ion suppression. Again, in complex biological samples from different individuals, or even the same individual at a different time, there may be large fluctuations in the concentrations of ion suppressing species. | 0 | Theoretical and Fundamental Chemistry |
Ste5 is a MAPK scaffold protein involved in the mating of yeast. The active complex is formed by interactions with the MAPK Fus3, the MAPK kinase (MAPKK) Ste7, and the MAPKK kinase Ste11. After the induction of mating by an appropriate mating pheromone (either a-factor or α –factor) Ste5 and its associated proteins are recruited to the membrane.
Ste4 helps to recruit Ste5, Ste4 is not required for the attachment of Ste5 to the membrane. Membrane association depends on a pleckstrin homology domain, as well as an amphipathic alpha-helical domain in the amino terminus.
During mating, Fus3 MAPK and Ptc1 phosphatase compete to control 4 phosphorylation sites on the Ste5 scaffold. When all of 4 sites have been dephosphorylated by Ptc1, Fus3 is released and becomes active.
Ste5 plays 2 main roles in the mating signal pathway:
#Binds the components of the MAPK cascade and holds them in an active complex
#Associates with the membrane, bringing the kinases to the membrane and promoting amplification of the signal (concentrating the bound kinases). Ste5 remains stably bound at the plasma membrane.
Ste5 oligomerization is very important for stable membrane recruitment. In one model, the activation of the pathway occurs at the same time that Ste5 is converted from a less active, closed form of Ste5 to an active Ste5 dimer that can bind to the beta-gamma subunit of the heterotrimeric G-protein and form a lattice for the MAPK cascade to assemble on.
Not only does Ste5 contribute to propagation of the pheromone signal, but it is also involved in down regulating of signalling. It stimulates autophosphorylation of Fus3, which results in phosphorylation of Ste5, causing a downregulation in signalling.
Ste5 also catalytically unlocks Fus3 (but not its homologue Kss1) for phosphorylation by Ste7. Both this catalytically active Ste5 domain as well as Ste7 are required for full Fus3 activation, which explains why Fus3 is activated by only the mating pathway, and remains inactive during other pathways which also utilize Ste7.
Ste5 can be localized to the cytoplasm, mating projection tip, nucleus, and plasma membrane. | 1 | Applied and Interdisciplinary Chemistry |
* [http://bascoe.oma.be/index.php/bascoe BASCOE] - A data assimilation system based on a chemical transport model and created by the Belgian Institute for Space Aeronomy (BIRA-IASB)
* [https://tropo.aeronomie.be/index.php/12-boream Boream] - Model for the degradation of alpha-pinene
* [https://www2.acom.ucar.edu/modeling/boxmox-box-model-extensions-kpp BOXMOX] - Box model extensions to KPP
* [https://doi.org/10.5194/gmd-14-2867-2021 CMAQ] - Community Multiscale Air Quality model
* [http://wiki.seas.harvard.edu/geos-chem/index.php/DSMACC_chemical_box_model DSMACC] - Dynamically Simple Model of Atmospheric Chemical Complexity
* [http://wiki.seas.harvard.edu/geos-chem/index.php/KPP_solvers_FAQ GEOS–Chem] - Global 3-D chemical transport model for atmospheric composition
* [https://www2.helsinki.fi/en/researchgroups/multi-scale-modelling/malte-box MALTE] - Model to predict new aerosol formation in the lower troposphere
* [http://mcm.york.ac.uk MCM] - Master Chemical Mechanism
* [http://www.mecca.messy-interface.org/ MECCA] - Module Efficiently Calculating the Chemistry of the Atmosphere
* [https://github.com/Mistra-UEA/Mistra Mistra] - Microphysical Stratus model
* [https://doi.org/10.1029/2021JD036140 PACT-1D] - Platform for Atmospheric Chemistry and vertical Transport in 1-dimension
* [https://palm.muk.uni-hannover.de/trac/wiki/doc/app/chemdesc PALM] - Meteorological modeling system for atmospheric and oceanic boundary layer flows
* [https://doi.org/10.1029/97JD00849 RACM] - Regional Atmospheric Chemistry Mechanism gas-phase chemistry mechanism
* [https://www2.acom.ucar.edu/wrf-chem WRF-Chem] - Weather Research & Forecasting Model with Chemistry | 0 | Theoretical and Fundamental Chemistry |
High-frequency vibrating screening equipment is a shaker whose frame is fixed and the drive vibrates only the screen cloth. High frequency vibration equipment is for particles that are in this particle size range of an 1/8 in (3 mm) down to a +150 mesh. Traditional shaker screeners have a difficult time making separations at sizes like 44 microns. At the same time, other high energy sieves like the Elcan Industries' advanced screening technology allow for much finer separations down to as fine as 10um and 5um, respectively.
These shakers usually make a secondary cut for further processing or make a finished product cut.
These shakers are usually set at a steep angle relative to the horizontal level plane. Angles range from 25 to 45 degrees relative to the horizontal level plane. | 1 | Applied and Interdisciplinary Chemistry |
Emilio Gino Segrè was born into a Sephardic Jewish family in Tivoli, near Rome, on 1 February 1905, the son of Giuseppe Segrè, a businessman who owned a paper mill, and Amelia Susanna Treves. He had two older brothers, Angelo and Marco. His uncle, Gino Segrè, was a law professor. He was educated at the ginnasio in Tivoli and, after the family moved to Rome in 1917, the ginnasio and liceo in Rome. He graduated in July 1922 and enrolled in the University of Rome La Sapienza as an engineering student.
In 1927, Segrè met Franco Rasetti, who introduced him to Enrico Fermi. The two young physics professors were looking for talented students. They attended the Volta Conference at Como in September 1927, where Segrè heard lectures from notable physicists including Niels Bohr, Werner Heisenberg, Robert Millikan, Wolfgang Pauli, Max Planck and Ernest Rutherford. Segrè then joined Fermi and Rasetti at their laboratory in Rome. With the help of the director of the Institute of Physics, Orso Mario Corbino, Segrè was able to transfer to physics, and, studying under Fermi, earned his laurea degree in July 1928, with a thesis on "Anomalous Dispersion and Magnetic Rotation".
After a stint in the Italian Army from 1928 to 1929, during which he was a commissioned as a second lieutenant in the antiaircraft artillery, Segrè returned to the laboratory on Via Panisperna. He published his first article, which summarised his thesis, "On anomalous dispersion in mercury and in lithium", jointly with Edoardo Amaldi in 1928, and another article with him the following year on the Raman effect.
In 1930, Segrè began studying the Zeeman effect in certain alkaline metals. When his progress stalled because the diffraction grating he required to continue was not available in Italy, he wrote to four laboratories elsewhere in Europe asking for assistance and received an invitation from Pieter Zeeman to finish his work at Zeemans laboratory in Amsterdam. Segrè was awarded a Rockefeller Foundation fellowship and, on Fermis advice, elected to use it to study under Otto Stern in Hamburg. Working with Otto Frisch on space quantization produced results that apparently did not agree with the current theory; but Isidor Isaac Rabi showed that theory and experiment were in agreement if the nuclear spin of potassium was +1/2. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, transamidification is the process of exchanging the subunits of a peptide, amide or ester compound with another amine or fatty acid to produce a new amide or peptide. The process has been used for the production of emulsifiers and dispersing agents and oil drilling fluids. | 0 | Theoretical and Fundamental Chemistry |
Tribocorrosion occurs in many engineering fields. It reduces the life-time of pipes, valves and pumps, of waste incinerators, of mining equipment or of medical implants, and it can affect the safety of nuclear reactors or of transport systems. On the other hand, tribocorrosion phenomena can also be applied to good use, for example in the chemical-mechanical planarization of wafers in the electronics industry or in metal grinding and cutting in presence of aqueous emulsions. Keeping this in mind, we may define tribocorrosion in a more general way independently of the notion of usefulness or damage or of the particular type of mechanical interaction: Tribocorrosion concerns the irreversible transformation of materials or of their function as a result of simultaneous mechanical and chemical/electrochemical interactions between surfaces in relative motion. | 1 | Applied and Interdisciplinary Chemistry |
Plant immune system activity is regulated in part by signaling hormones such as:
* Salicylic acid
* Jasmonic acid
* Ethylene
There can be substantial cross-talk among these pathways. | 1 | Applied and Interdisciplinary Chemistry |
Mycosporine-like amino acids are small secondary metabolites produced by organisms that live in environments with high volumes of sunlight, usually marine environments. | 1 | Applied and Interdisciplinary Chemistry |
A mitogen is a small bioactive protein or peptide that induces a cell to begin cell division, or enhances the rate of division (mitosis). Mitogenesis is the induction (triggering) of mitosis, typically via a mitogen. The mechanism of action of a mitogen is that it triggers signal transduction pathways involving mitogen-activated protein kinase (MAPK), leading to mitosis. | 1 | Applied and Interdisciplinary Chemistry |
As many quantities of cell biological interest are present in discrete copy number within the cell (single DNAs, dozens of mRNAs, hundreds of proteins), tools from discrete stochastic mathematics are often used to analyse and model cellular noise. In particular, master equation treatments – where the probabilities of observing a system in a state at time are linked through ODEs – have proved particularly fruitful. A canonical model for noise gene expression, where the processes of DNA activation, transcription and translation are all represented as Poisson processes with given rates, gives a master equation which may be solved exactly (with generating functions) under various assumptions or approximated with stochastic tools like Van Kampen's system size expansion.
Numerically, the Gillespie algorithm or stochastic simulation algorithm is often used to create realisations of stochastic cellular processes, from which statistics can be calculated.
The problem of inferring the values of parameters in stochastic models (parametric inference) for biological processes, which are typically characterised by sparse and noisy experimental data, is an active field of research, with methods including Bayesian MCMC and approximate Bayesian computation proving adaptable and robust. Regarding the two-state model, a moment-based method was described for parameters inference from mRNAs distributions. | 1 | Applied and Interdisciplinary Chemistry |
Diffusion of gases is configured with a uniform concentration of gases and while the gases are stationary. Diffusion is the change of concentration between the two gases due to a weaker concentration gradient between the two gases. Diffusion is the transportation of mass over a period of time. | 1 | Applied and Interdisciplinary Chemistry |
Stormwater management occurs on a watershed scale to prevent downstream impacts on urban water quality. A watershed is maintained through the cyclical accumulation, storage, and flow of groundwater. Naturally occurring watersheds are damaged when they are sealed by an impervious surface, which diverts pollutant-carrying stormwater runoff into streams. Urban watersheds are affected by greater quantities of pollutants due to the consequences of anthropogenic activities within urban environments. Rainfall on impermeable surfaces accumulates surface runoff containing oil, bacteria, and sediment that eventually makes its way to streams and groundwater. Stormwater control strategies such as infiltration gardens treat contaminated surface runoff and return processed water to the underlying soil, helping to restore the watershed system. The effectiveness of stormwater control systems is measured by the reduction of the amount of rainfall that becomes runoff (retention), and the lag time (rate of depletion) of the runoff. Even rain gardens with small capacities for daily infiltration can create a positive cumulative impact on mitigating urban runoff. Increasing the number of permeable surfaces by designing rain gardens reduces the amount of polluted stormwater that reaches natural bodies of water and recharges groundwater at a higher rate. Additionally, adding a rain garden to a site that experiences excessive rainwater runoff mitigates the water quantity load on public stormwater systems.
The bioretention approach to water treatment, and specifically rain gardens in this context, is two-fold: to utilize the natural processes within landscapes and soils to transport, store, and filter stormwater before it becomes runoff, and to reduce the overall amount of impervious surface covering the ground that allow for contaminated urban runoff. Rain gardens perform most effectively when they interact with the greater system of stormwater control. This integrated approach to water treatment is called the "stormwater chain", which consists of all associated techniques to prevent surface run-off, retain run-off for infiltration or evaporation, detain run-off and release it at a predetermined rate, and convey rainfall from where it lands to detention or retention facilities. Rain gardens have many reverberating effects on the greater hydrological system. In a bioretention system such as a rain garden, water filters through layers of soil and vegetation media, which treat the water before it enters the groundwater system or an underdrain. Any remaining runoff from a rain garden will have a lower temperature than runoff from an impervious surface, which reduces the thermal shock on receiving bodies of water. Additionally, increasing the amount of permeable surfaces by designing urban rain gardens reduces the amount of polluted stormwater that reaches natural bodies of water and recharges groundwater at a higher rate. | 1 | Applied and Interdisciplinary Chemistry |
Recent work has investigated the role of enhancers in morphological changes in threespine stickleback fish. Sticklebacks exist in both marine and freshwater environments, but sticklebacks in many freshwater populations have completely lost their pelvic fins (appendages homologous to the posterior limb of tetrapods).<br> Pitx1 is a homeobox gene involved in posterior limb development in vertebrates. Preliminary genetic analyses indicated that changes in the expression of this gene were responsible for pelvic reduction in sticklebacks. Fish expressing only the freshwater allele of Pitx1 do not have pelvic spines, whereas fish expressing a marine allele retain pelvic spines. A more thorough characterization showed that a 500 base pair enhancer sequence is responsible for turning on Pitx1 expression in the posterior fin bud. This enhancer is located near a chromosomal fragile site—a sequence of DNA that is likely to be broken and thus more likely to be mutated as a result of imprecise DNA repair. This fragile site has caused repeated, independent losses of the enhancer responsible for driving Pitx1 expression in the pelvic spines in isolated freshwater population, and without this enhancer, freshwater fish fail to develop pelvic spines. | 1 | Applied and Interdisciplinary Chemistry |
The Urbach tail is an exponential part in the energy spectrum of the absorption coefficient. This tail appears near the optical band edge in amorphous, disordered and crystalline materials. | 0 | Theoretical and Fundamental Chemistry |
Investment casting (known as lost-wax casting in art) is a process that has been practiced for thousands of years, with the lost-wax process being one of the oldest known metal forming techniques. From 5000 years ago, when beeswax formed the pattern, to today's high technology waxes, refractory materials, and specialist alloys, the castings ensure high-quality components are produced with the key benefits of accuracy, repeatability, versatility, and integrity.
Investment casting derives its name from the fact that the pattern is invested, or surrounded, with a refractory material. The wax patterns require extreme care for they are not strong enough to withstand forces encountered during the mold making. One advantage of investment casting is that the wax can be reused.
The process is suitable for repeatable production of net shape components from a variety of different metals and high performance alloys. Although generally used for small castings, this process has been used to produce complete aircraft door frames, with steel castings of up to 300 kg and aluminium castings of up to 30 kg. Compared to other casting processes such as die casting or sand casting, it can be an expensive process. However, the components that can be produced using investment casting can incorporate intricate contours, and in most cases the components are cast near net shape, so require little or no rework once cast. | 1 | Applied and Interdisciplinary Chemistry |
Sources:
The G equation reads as
where
* is the flow velocity field
* is the local burning velocity
The flame location is given by which can be defined arbitrarily such that is the region of burnt gas and is the region of unburnt gas. The normal vector to the flame is . | 1 | Applied and Interdisciplinary Chemistry |
This timeline of nuclear fusion is an incomplete chronological summary of significant events in the study and use of nuclear fusion. | 0 | Theoretical and Fundamental Chemistry |
Room temperature, colloquially, denotes the range of air temperatures most people find comfortable indoors while dressed in typical clothing. These temperatures feel comfortable to people wearing typical indoor clothing. But comfortable temperatures can be extended beyond this range depending on humidity, air circulation, and other factors.
In certain fields, like science and engineering, and within a particular context, room temperature can mean different agreed-upon ranges. In contrast, ambient temperature is the actual temperature, as measured by a thermometer, of the air (or other medium and surroundings) in any particular place. The ambient temperature (e.g. an unheated room in winter) may be very different from an ideal room temperature.
Food or beverages may be served at "room temperature", meaning neither heated nor cooled. | 1 | Applied and Interdisciplinary Chemistry |
Lack of funding is consistently cited as a barrier to the implementation of green infrastructure. One advantage that green infrastructure projects offer, however, is that they generate so many benefits that they can compete for a variety of diverse funding sources. Some tax incentive programs administered by federal agencies can be used to attract financing to green infrastructure projects. Here are two examples of programs whose missions are broad enough to support green infrastructure projects:
* The U.S. Department of Energy administers a range of energy efficiency tax incentives, and green infrastructure could be integrated into project design to claim the incentive. An example of how this might work is found in Oregon's Energy Efficiency Construction Credits. In Eugene, Oregon, a new biofuel station built on an abandoned gas station site included a green roof, bioswales and rain gardens. In this case, nearly $250,000 worth of tax credits reduced income and sales tax for the private company that built and operated the project.
* The U.S. Department of Treasury administers the multibillion-dollar New Markets Tax Credit Program, which encourages private investment for a range of project types (typically real estate or business development projects) in distressed areas. Awards are allocated to non-profit and private entities based on their proposals for distributing these tax benefits. | 1 | Applied and Interdisciplinary Chemistry |
Lexitropsins are members of a family of semi-synthetic DNA-binding ligands. They are structural analogs of the natural antibiotics netropsin and distamycin. Antibiotics of this group can bind in the minor groove of DNA with different sequence-selectivity. Lexitropsins form a complexes with DNA with stoichiometry 1:1 and 2:1. Based on the 2:1 complexes were obtained ligands with high sequence-selectivity. | 1 | Applied and Interdisciplinary Chemistry |
Sputtering only happens when the kinetic energy of the incoming particles is much higher than conventional thermal energies (≫ 1 eV). When done with direct current (DC sputtering), voltages of 3-5 kV are used. When done with alternating current (RF sputtering), frequencies are around the 14 MHz range. | 0 | Theoretical and Fundamental Chemistry |
Photosensitization, i.e., photochemical sensitization. Exposing dyed cellulosic material, such as plant-based fibers, to sunlight allows dyes to remove hydrogen from the cellulose, resulting in photoreduction on the cellulosic substrate. Simultaneously, the colorant will undergo oxidation in the presence of the atmospheric oxygen, resulting in photo-oxidation of the colourant. These processes result in both fading of the colorant and strength loss of the substrate. | 0 | Theoretical and Fundamental Chemistry |
2-methylisocitric acid, an intermediate of the methylcitrate cycle, was first synthesized in 1886 as a mixture of four isomers. The pathway of the methylcitrate cycle was not discovered until 1973 in fungi, though it was not yet fully understood. Originally, the methylcitrate cycle was thought to be present only in fungal species, such as Candida lipolytica and Aspergillus nidulans. In 1999, it was discovered that the methylcitrate cycle was also present in bacteria Salmonella enterica and Escherichia coli. Much research has been done on the methylcitrate cycle's role in the development and function of various fungi and strains of bacteria, as well as its virulent properties in conjunction with the glyoxylate cycle. | 1 | Applied and Interdisciplinary Chemistry |
A significant achievement of Lecoq de Boisbaudran was his discovery of the element gallium in 1875. Beginning in 1874, Lecoq de Boisbaudran investigated a sample of 52 kg of the mineral ore sphalerite obtained from the Pierrefitte mine in the Pyrenees. From it, he extracted several milligrams of gallium chloride. Using spectroscopic methods, he observed what appeared to be two previously unreported lines in the sample's spectrum, at wavelengths of 4170 and 4031 angstroms.
He continued his experiments using several hundred kilograms of crude zinc ore and in the same year isolated more than one gram of a near-pure metal by electrolysis of a solution of the metal in its form as a hydroxide compound, dissolved in potassium hydroxide solution. Later he prepared 75 grams of gallium using more than 4 tonnes of crude ore. He confirmed its spectral characteristics, consisting of two spectral lines in the violet portion of the spectrum of the mineral sphalerite. In this way, he ruled out the possibility that the spectral characteristics were an accident of the extraction process, rather than being an indication of a new element.
He named his discovery "gallium", from the Latin Gallia meaning Gaul, in honor of his native land of France. It was later suggested that Lecoq de Boisbaudran had named the element after himself, since gallus is the Latin translation of the French le coq. Lecoq de Boisbaudran denied this suggestion in an article in 1877. He published an account of his investigations on the new element in Sur un nouveau metal, le gallium (1877).
De Boisbaudran calculated the atomic mass of gallium as 69.86, close to the currently accepted value of 69.723. Unknown to Lecoq de Boisbaudran, the existence of gallium had been predicted during 1871 by Dmitri Mendeleev, who gave it the name eka-aluminium. De Boisbaudrans discovery of gallium was significant support for Mendeleevs theory of the periodicity of the elements. | 1 | Applied and Interdisciplinary Chemistry |
Aside from using an Olszewski tube and hypolimnetic withdrawal, there are other techniques implemented to achieve the same goals as an Olszewski tube. These include increasing dissolved oxygen, reducing nutrient concentration, and lessening the amount of algae and unwanted biomass in lakes.
* Sediment oxidation is the artificial oxidation of the top 15 to 20 centimeters of anaerobic lake sediment. This technique reduces internal nutrient release through a series of chemical reactions starting with iron(III) chloride. After these reactions, the concentrations of phosphorus and ammonium (another nutrient found in lakes) decrease and the demand for oxygen gas in reduced as well. This technique is still not fully developed yet but can mirror the effects of the Olszewski tube.
* Biological control methods are the most promising techniques because they do the least harm to the ecosystem. These methods introduce a particular species (e.g. fish, bacteria, etc.) into a lake as a solution to a current problem. The introduction of a certain type of bacteria can help decrease nutrients. In turn the algae will not spread and the oxygen in the lake will stay in high dissolved concentrations.
* Hypolimnetic aeration is another technique in which oxygen is added to the lake. This helps increase the concentration of dissolved oxygen in the lake as well as bring down the levels of phosphorus. While the results of this technique are similar to those of the Olszewski tube, hypolimnetic aeration differs in that it uses compressed air to move the water rather than a siphoning effect. | 1 | Applied and Interdisciplinary Chemistry |
In 2002, Tang was awarded a Japan Society for the Promotion of Science (JSPS) search Fellowship and NIMS Researcher, enable to expand his research in photocatalysis in the National Institute for Materials Science (NIMS), Japan. In 2005, he was appointed as a senior research associate in the Department of Chemistry at Imperial College London, UK.
In 2009, Tang was appointed as a lecturer in energy (permanent position) in Department of Chemical Engineering at University College London, then promoted to a senior lecturer in 2011, a readership in 2014 and finally a full professor of materials chemistry and engineering in 2017. During this period, he was also appointed as the director of University Materials Hub. In 2022, Tang moved from UCL to Tsinghua University.
Tang is a member of the Academy of Europe / Academia Europaea, a Royal Society Leverhulme Trust Senior Research Fellow, a Fellow of European Academy of Sciences, a Fellow of Royal Society of Chemistry. He also sits on the editorial board of four international journals, e.g. editor of Applied Catalysis B : Environmental, editor-in-chief of Journal of Advanced Chemical Engineering, associate editor of Asia-Pacific Journal of Chemical Engineering and associate editor of Chin Journal of Catalysis, as well as a member of the committees of the RSC Chemical Nanoscience & Nanotechnology. He also sits on the panel of a few counties’ National Science Foundations. | 0 | Theoretical and Fundamental Chemistry |
Notable research units includes:
* Photovoltaic Energy Development and Research Institute, École nationale supérieure de chimie de Paris in association with the CNRS. Director Olivier Kerrec and research director Daniel Lincot. | 1 | Applied and Interdisciplinary Chemistry |
Although the vast majority of seawater has a salinity of between 31 and 38 g/kg, that is 3.1–3.8%, seawater is not uniformly saline throughout the world. Where mixing occurs with freshwater runoff from river mouths, near melting glaciers or vast amounts of precipitation (e.g. monsoon), seawater can be substantially less saline. The most saline open sea is the Red Sea, where high rates of evaporation, low precipitation and low river run-off, and confined circulation result in unusually salty water. The salinity in isolated bodies of water can be considerably greater still about ten times higher in the case of the Dead Sea. Historically, several salinity scales were used to approximate the absolute salinity of seawater. A popular scale was the "Practical Salinity Scale" where salinity was measured in "practical salinity units (PSU)". The current standard for salinity is the "Reference Salinity" scale with the salinity expressed in units of "g/kg". | 0 | Theoretical and Fundamental Chemistry |
* Identification of novel modified sites – BoMoC does not capture the modification directly but rather the mis-incorporation signature resulting from the modified base. Therefore, sites where modification status has not been previously established may be difficult to confirm the identity of the modification.
* Pre-mature termination of cDNA – Approximately, 10% of miRNA species characterized using OTTR experience prematurely terminated cDNA products. While these levels are low compared to common reverse transcriptase, some species carrying very bulky modifications may be challenging to capture with OTTR.
* Diversity in species used for benchmarking – To date, miRNA and tRNA pools have been characterized with OTTR. However, more validation, with diverse RNA and DNA species will increase the potential applications of OTTR. | 1 | Applied and Interdisciplinary Chemistry |
MIKE 11 has been used in hundreds of application around the world. Its main application areas are flood analysis and alleviation design, real-time flood forecasting, dam break analysis, optimisation of reservoir and canal gate/structure operations, ecological and water quality assessments in rivers and wetlands, sediment transport and river morphology studies, salinity intrusion in rivers and estuaries. | 1 | Applied and Interdisciplinary Chemistry |
Boats are traditionally piloted from starboard (the right-hand side) to facilitate priority to the right.
According to the International Regulations for Preventing Collisions at Sea, water traffic is effectively RHT: a vessel proceeding along a narrow channel must keep to starboard, and when two power-driven vessels are meeting head-on both must alter course to starboard also. | 0 | Theoretical and Fundamental Chemistry |
Cavitation is the formation of vapour bubbles in liquid caused by flow around an object. Bubbles form when water accelerates around sharp corners and the pressure drops below the vapour pressure. Pressure increases upon deceleration, and the water generally reabsorbs the vapour; however, vapour bubbles can implode and apply small concentrated impulses that may damage surfaces like ship propellers and pump impellers.
The potential for vapour bubbles to form in a liquid is given by the nondimensional cavitation number. It equals local pressure minus vapour pressure, divided by dynamic pressure. At increasing depths (or pressures in piping), the potential for cavitation is lower because the difference between local pressure and vapour pressure is greater.
A supercavitating object is a high-speed submerged object that is designed to initiate a cavitation bubble at its nose. The bubble extends (either naturally or augmented with internally generated gas) past the aft end of the object and prevents contact between the sides of the object and the liquid. This separation substantially reduces the skin friction drag on the supercavitating object.
A key feature of the supercavitating object is the nose, which typically has a sharp edge around its perimeter to form the cavitation bubble. The nose may be articulated and shaped as a flat disk or cone. The shape of the supercavitating object is generally slender so the cavitation bubble encompasses the object. If the bubble is not long enough to encompass the object, especially at slower speeds, the bubble can be enlarged and extended by injecting high-pressure gas near the object's nose.
The very high speed required for supercavitation can be temporarily reached by underwater-fired projectiles and projectiles entering water. For sustained supercavitation, rocket propulsion is used, and the high-pressure rocket gas can be routed to the nose to enhance the cavitation bubble. In principle, supercavitating objects can be maneuvered using various methods, including the following:
* Drag fins that project through the bubble into the surrounding liquid
* A tilted object nose
* Gas injected asymmetrically near the nose to distort the cavity's geometry
* Vectoring rocket thrust through gimbaling for a single nozzle
* Differential thrust from multiple nozzles | 1 | Applied and Interdisciplinary Chemistry |
The conventional photo-reflectance experimental setup uses a xenon or tungsten based lamp source passed through a monochromator to form the incident probe beam. The pump beam may be formed by the output of a continuous wave (CW) laser (e.g. a He-Ne or He-Cd laser) passed through a chopper wheel, or may be formed by the output of a directly modulated semiconductor diode laser. The pump beam is focused to a spot on the sample where it interacts with the sample. The probe beam is co-focused onto the sample where it is reflected. The reflected probe beam is collected and passed through an optical filter to eliminate any unwanted pump light and/or photoluminescence signal. Thereafter the probe beam is directed onto a photodetector (e.g. a Si or InGaAs photodiode), which converts the probe intensity to an electrical signal. The electrical signal is processed to eliminate unwanted noise, typically using a lock-in circuit referenced to the modulation frequency. The photo-reflectance signal is then recorded as a function of probe beam wavelength using a computer or the like. | 0 | Theoretical and Fundamental Chemistry |
TERRA in biology is an abbreviation for "TElomeric Repeat-containing RNA". TERRA is RNA that is transcribed from telomeres — the repeating 6-nucleotide sequences that cap the ends of chromosomes. TERRA functions with shelterin to inhibit telomere lengthening by enzyme telomerase. However, other studies have shown that under certain conditions TERRA can recruit telomerase to telomeres.
TERRAs are essential for telomere length and maintenance. At least four factors contribute to telomere maintenance: telomerase, shelterin, TERRA and the CST Complex.
TERRA can also regulate telomere length by increasing euchromatin formation. On the other hand, nonsense-mediated decay factor enrichment at telomeres may exist to prevent TERRA inhibition of telomerase. TERRA levels vary during the cell cycle, decreasing during S phase, and increasing in the transition from G2 phase to G1 phase. | 1 | Applied and Interdisciplinary Chemistry |
The general formula for the action of an element of a space group is
: y = M.x + D
where M is its matrix, D is its vector, and where the element transforms point x into point y. In general, D = D (lattice) + , where is a unique function of M that is zero for M being the identity. The matrices M form a point group that is a basis of the space group; the lattice must be symmetric under that point group, but the crystal structure itself may not be symmetric under that point group as applied to any particular point (that is, without a translation). For example, the diamond cubic structure does not have any point where the cubic point group applies.
The lattice dimension can be less than the overall dimension, resulting in a "subperiodic" space group. For (overall dimension, lattice dimension):
* (1,1): One-dimensional line groups
* (2,1): Two-dimensional line groups: frieze groups
* (2,2): Wallpaper groups
* (3,1): Three-dimensional line groups; with the 3D crystallographic point groups, the rod groups
* (3,2): Layer groups
* (3,3): The space groups discussed in this article | 0 | Theoretical and Fundamental Chemistry |
International trade and water is the relationship between international trade and the water being used by humans. The substantial increase in human population during the 20th century combined with rapid increases in overall global economic development has resulted in rising challenges for the future of public water management. The developing world has been particularly impacted by the lack of access to clean water. Each year, millions of people die due to illnesses, diseases, and lack the capital to create the infrastructure necessary to combat the problem. These conditions have increased the global demand for clean water and in turn, have pressured free market economists to suggest that wealthy market players are the most efficient solution to addressing water issues. Several nations can benefit from international trade in water. Particularly nations with excess fresh water and abundant capital are looking forward to making healthy profits from either the export of water to other nations, or are interested in the investment returns they will earn from participation in foreign markets. However, not everyone agrees that market forces are best capable of solving water issues. NGOs, human rights organizations, and various stakeholders oppose viewing water in economic terms. These individuals accuse international trade agreements and international economic institutions including the World Bank and the International Monetary Fund (IMF) of attempting to privatize a resource that they consider a basic human right. The lack of a common understanding of whether or not water should be viewed as a commodity or a basic human right has resulted in heated debates among legal professionals and leading members of the academia. | 1 | Applied and Interdisciplinary Chemistry |
The valley or wadi of Nahal Mishmar begins in the Hebron hills, running east towards the Dead Sea. Its western part is shallow, at an altitude of approximately 270 m above sea level, and it proceeds to fall more than 300 meters into the Jordan Rift Valley before emptying into the Dead Sea, over . Nahal Mishmar runs north of the Tze'elim Stream, between Ein Gedi and Masada.
Access is from Highway 90. | 1 | Applied and Interdisciplinary Chemistry |
NADH:ubiquinone oxidoreductase is the largest of the respiratory complexes. In mammals, the enzyme contains 44 separate water-soluble peripheral membrane proteins, which are anchored to the integral membrane constituents. Of particular functional importance are the flavin prosthetic group (FMN) and eight iron-sulfur clusters (FeS). Of the 44 subunits, seven are encoded by the mitochondrial genome.
The structure is an "L" shape with a long membrane domain (with around 60 trans-membrane helices) and a hydrophilic (or peripheral) domain, which includes all the known redox centres and the NADH binding site. All thirteen of the E. coli proteins, which comprise NADH dehydrogenase I, are encoded within the nuo operon, and are homologous to mitochondrial complex I subunits. The antiporter-like subunits NuoL/M/N each contains 14 conserved transmembrane (TM) helices. Two of them are discontinuous, but subunit NuoL contains a 110 Å long amphipathic α-helix, spanning the entire length of the domain. The subunit, NuoL, is related to Na/ H antiporters of [http://tcdb.org/search/result.php?tc=2.A.63.1.1 TC# 2.A.63.1.1] (PhaA and PhaD).
Three of the conserved, membrane-bound subunits in NADH dehydrogenase are related to each other, and to Mrp sodium-proton antiporters. Structural analysis of two prokaryotic complexes I revealed that the three subunits each contain fourteen transmembrane helices that overlay in structural alignments: the translocation of three protons may be coordinated by a lateral helix connecting them.
Complex I contains a ubiquinone binding pocket at the interface of the 49-kDa and PSST subunits. Close to iron-sulfur cluster N2, the proposed immediate electron donor for ubiquinone, a highly conserved tyrosine constitutes a critical element of the quinone reduction site. A possible quinone exchange path leads from cluster N2 to the N-terminal beta-sheet of the 49-kDa subunit. All 45 subunits of the bovine NDHI have been sequenced. Each complex contains noncovalently bound FMN, coenzyme Q and several iron-sulfur centers. The bacterial NDHs have 8-9 iron-sulfur centers.
A recent study used electron paramagnetic resonance (EPR) spectra and double electron-electron resonance (DEER) to determine the path of electron transfer through the iron-sulfur complexes, which are located in the hydrophilic domain. Seven of these clusters form a chain from the flavin to the quinone binding sites; the eighth cluster is located on the other side of the flavin, and its function is unknown. The EPR and DEER results suggest an alternating or “roller-coaster” potential energy profile for the electron transfer between the active sites and along the iron-sulfur clusters, which can optimize the rate of electron travel and allow efficient energy conversion in complex I.
Notes:
* Found in all species except fungi
* May or may not be present in any species
* Found in fungal species such as Schizosaccharomyces pombe
* Recent research has described NDUFA4 to be a subunit of complex IV, and not of complex I | 1 | Applied and Interdisciplinary Chemistry |
The refrigerant naming system is mainly used for fluorinated and chlorinated short alkanes used as refrigerants. In the United States, the standard is specified in ANSI/ASHRAE Standard 34–1992, with additional annual supplements. The specified ANSI/ASHRAE prefixes were FC (fluorocarbon) or R (refrigerant), but today most are prefixed by a more specific classification:
*CFC—list of chlorofluorocarbons
*HCFC—list of hydrochlorofluorocarbons
*HFC—list of hydrofluorocarbons
*FC—list of fluorocarbons
*PFC—list of perfluorocarbons (completely fluorinated)
The decoding system for CFC-01234a is:
*0 = Number of double bonds (omitted if zero)
*1 = Carbon atoms -1 (omitted if zero)
*2 = Hydrogen atoms +1
*3 = Fluorine atoms
*4 = Replaced by Bromine ("B" prefix added)
*a = Letter added to identify isomers, the "normal" isomer in any number has the smallest mass difference on each carbon, and a, b, or c are added as the masses diverge from normal.
Other coding systems are in use as well. | 1 | Applied and Interdisciplinary Chemistry |
Several photons of energy below the ionization threshold may actually combine their energies to ionize an atom. This probability decreases rapidly with the number of photons required, but the development of very intense, pulsed lasers still makes it possible. In the perturbative regime (below about 10 W/cm at optical frequencies), the probability of absorbing N photons depends on the laser-light intensity I as I.
Above threshold ionization (ATI) is an extension of multi-photon ionization where even more photons are absorbed than actually would be necessary to ionize the atom. The excess energy gives the released electron higher kinetic energy than the usual case of just-above threshold ionization. More precisely, the system will have multiple peaks in its photoelectron spectrum which are separated by the photon energies, this indicates that the emitted electron has more kinetic energy than in the normal (lowest possible number of photons) ionization case. The electrons released from the target will have approximately an integer number of photon-energies more kinetic energy. In intensity regions between 10 W/cm and 10 W/cm, each of MPI, ATI, and barrier suppression ionization can occur simultaneously, each contributing to the overall ionization of the atoms involved. | 0 | Theoretical and Fundamental Chemistry |
After serving in the US Navy, Phelps worked at chemical instrument company Cole-Parmer in Chicago, Illinois, but a year later, not liking the cold Chicago climate, she returned to Tennessee. In June 2009, Phelps joined Oak Ridge National Laboratory. She started as a technician and was later promoted to research associate and program manager. Phelps works in the Nuclear Science and Engineering Directorate as the project manager for the nickel-63 and selenium-75 industrial isotope programs. As a member of Oak Ridge's Nuclear Materials Processing Group, she is part of the research and development staff, working with "super heavy" transuranic isotopes that are produced mainly by nuclear transmutation. She is also a member of the Medical, Industrial and Research Isotopes Group, where she researches elements such as actinium, lanthanum, europium, and samarium.
Phelps was involved in the discovery of the second-heaviest known element, tennessine (element 117). She was part of a three-month process to purify 22 mg of berkelium-249, which was shipped to the Joint Institute for Nuclear Research and combined with calcium-48 in a fusion reaction to create tennessine. In IUPAC's crediting Oak Ridge laboratory collectively as principal co-discoverer of tennessine, it acknowledged 61 individuals at ORNL who had contributed to the project including members of operations staff, support personnel, and researchers such as Phelps. It recognized Phelps as the first African-American woman involved with the discovery of a chemical element.
When Oak Ridge National Laboratory held a gala to honor and celebrate the team that discovered tennessine, Phelps's name was left off the list, and when she showed up, she cried as she realized that she did not have a seat at the table with the other scientists. In addition, a plaque to commemorate the discovery was created to be hung up in perpetuity at the laboratory, and once again, it omitted her name. Phelps was told that her name had been cut off by mistake due to a line break in a spreadsheet. While the laboratory later claimed that the "error [was] quickly corrected", it was only after Phelps fought for several months to have her name included that the laboratory acquiesced.
Phelps has contributed to additional research efforts, including those of spectroscopic analysis and spectrophotometric valence state studies of plutonium-238 and neptunium-237 and 238 for the National Aeronautic and Space Administration (NASA). Phelps has also studied electrodeposition with californium-252 for the Californium Rare Isotope Breeder Upgrade project.
Phelps is a member of the American Chemical Society. | 0 | Theoretical and Fundamental Chemistry |
The carboalumination reaction is most commonly catalyzed by zirconocene dichloride (or related catalyst). Some carboaluminations are performed with titanocene complexes. This reaction is sometimes referred to as the Zr- catalyzed asymmetric carboalumination of alkenes (ZACA) or the Zr-catalyzed methylalumination of alkynes (ZMA).
The most common trialkyl aluminum reagents for this transformation are trimethylaluminium, triethylaluminium, and sometimes triisobutylaluminium. When using trialkylaluminum reagents that have beta-hydrides, eliminations and hydroaluminum reactions become competing processes. The general mechanism of the ZMA reaction can be described as first the formation of the active catalytic species from the pre-catalyst zirconocene dichloride through its reaction with trimethyl aluminum. First transmetalation of a methyl from the aluminum to the zirconium occurs. Next, chloride abstraction by aluminum creates a cationic zirconium species that is closely associated with an anionic aluminum complex. This zirconium cation can coordinate an alkene or alkyne where migratory insertion of a methyl then takes place. The resultant vinyl or alkyl zirconium species can undergo a reversible, but stereoretentive transmetalation with an organoaluminum to provide the carboalumination product and regeneration of the zirconcene dichloride catalyst. This process generally provides the syn-addition product; however, conditions exist to provide the anti-addition product though a modified mechanism.
Trimethylsilyl (TMS) protected alkynes, trimethyl germanium alkynes, and terminal alkynes can produce anti-carboalumination products at room temperature or elevated temperatures if a coordinating group is nearby on the substrate. In these reactions, first syn-carboalumination takes place under the previously outlined mechanism. Then, another equivalent of aluminum that is coordinated to the directing group can displace the vinyl aluminum, inverting the geometry at the carbon where displacement takes place.
This forms a thermodynamically favorable metallacycle to prevent subsequent inversions. Formally, this process provides anti-carboalumination products that can be quenched with electrophiles. A limitation of this methodology is that the directing group must be sufficiently close to the carbon-carbon π-bond to form a thermodynamically favorable ring or else mixtures of geometric isomers will form.
The carboalumination of alkenes to form substituted alkanes can be rendered enantioselective if prochiral alkenes are used. In these reactions, a chiral indenyl zirconium catalyst is used to induce enantioselectivity. In these reactions, high enantioselectivities were obtained for several trialkyl aluminum reagents, however, the yield decreases dramatically with each additional carbon of the alkyl chain on the trialkyl aluminum reagent. | 0 | Theoretical and Fundamental Chemistry |
Single crystal polymers have unique applications in various fields Compared to single crystals of small molecules. Because of the long chain and various conformation, it is hard for the polymers to be crystallized directly from solution. Few examples of polymer single crystals prepared in this way suffered from low quality and small size. Topochemical polymerization provides a potential solution to yield high-quality polymer single crystals.
If the polymer is still mono crystalline, the transformation from single-crystal monomer to polymer is called single-crystal-to-single-crystal (SCSC) transformation, which required a more sophisticated design than normal topochemical polymerization. In order to prevent the polymer from breaking into polycrystalline powder, the stress-releasing strategies should be carefully considered. However, the study on general criteria of SCSC transition is still in its infancy and requires further study. | 0 | Theoretical and Fundamental Chemistry |
A ligand-targeted liposome (LTL) is a nanocarrier with specific ligands attached to its surface to enhance localization for targeted drug delivery. The targeting ability of LTLs enhances cellular localization and uptake of these liposomes for therapeutic or diagnostic purposes. LTLs have the potential to enhance drug delivery by decreasing peripheral systemic toxicity, increasing in vivo drug stability, enhancing cellular uptake, and increasing efficiency for chemotherapeutics and other applications. Liposomes are beneficial in therapeutic manufacturing because of low batch-to-batch variability, easy synthesis, favorable scalability, and strong biocompatibility. Ligand-targeting technology enhances liposomes by adding targeting properties for directed drug delivery. | 1 | Applied and Interdisciplinary Chemistry |
Policies in the United States have included a decrease in the subsidies provided by the federal and state governments to the oil industry which have usually included $2.84 billion. This is more than what is actually set aside for the biofuel industry. The measure was discussed at the G20 in Pittsburgh where leaders agreed that "inefficient fossil fuel subsidies encourage wasteful consumption, reduce our energy security, impede investment in clean sources and undermine efforts to deal with the threat of climate change". If this commitment is followed through and subsidies are removed, a fairer market in which algae biofuels can compete will be created. In 2010, the U.S. House of Representatives passed a legislation seeking to give algae-based biofuels parity with cellulose biofuels in federal tax credit programs. The algae-based renewable fuel promotion act (HR 4168) was implemented to give biofuel projects access to a $1.01 per gal production tax credit and 50% bonus depreciation for biofuel plant property. The U.S Government also introduced the domestic Fuel for Enhancing National Security Act implemented in 2011. This policy constitutes an amendment to the Federal property and administrative services act of 1949 and federal defense provisions in order to extend to 15 the number of years that the Department of Defense (DOD) multiyear contract may be entered into the case of the purchase of advanced biofuel. Federal and DOD programs are usually limited to a 5-year period | 1 | Applied and Interdisciplinary Chemistry |
Surfactin is a cyclic lipopeptide, commonly used as an antibiotic for its capacity as a surfactant. It is an amphiphile capable of withstanding hydrophilic and hydrophobic environments. The Gram-positive bacterial species Bacillus subtilis produces surfactin for its antibiotic effects against competitors. Surfactin showcases antibacterial, antiviral, antifungal, and hemolytic effects. | 0 | Theoretical and Fundamental Chemistry |
Biodiversity refers to the variety of life forms, including species diversity, genetic diversity, and ecosystem diversity. The Great Barrier Reef is a biodiversity hotspot, ranging over 9000 known species. However, since the 1950’s half of the living corals on the Great Barrier Reef have died, and coral reef-associated biodiversity has declined by sixty three percent. Only an estimated twenty five percent of these species have been formally discovered, leaving a substantial proportion yet to be scientifically classified. We are no doubt losing species we have yet to identify in the wake of a shifting climate.
Reduced levels of aragonite, as a result of ocean acidification, continues to be one of the Great Barrier Reef's biggest threats. Healthy reefs support thousands of different corals, fish and marine mammals, but bleached reefs lose their ability to support and sustain life. Coral structural formations create complex habitats critical for providing shelter, breeding grounds, and food sources for numerous marine organisms, including fish, invertebrates, and microorganisms. In turn, corals depend on reef fish and other organisms to clean and regulate algae levels, provide nutrients for coral growth, and keep pests in check. Coral reefs and the species they host have dynamic symbiotic relationships.
Ocean acidification can also indirectly affect any organism, having reduced growth rates, decreased reproductive capacity, increased susceptibility to disease, and elevated mortality rates. Bleaching events trigger homogenization of coral composition and losses of structural complexity which can be detrimental to reef fish and other organisms that depend on branching coral for breeding and shelter. This decrease in ecosystem diversity has direct effects on species diversity. | 0 | Theoretical and Fundamental Chemistry |
After water mains are in service for a long time, there will be deterioration in structural, water quality, and hydraulic performance. Structural deterioration may be caused by many factors. Metal-based pipes develop internal and external corrosion, causing the pipe walls to thin or degrade. They can eventually leak or burst. Cement-based pipes are subject to cement matrix and reinforced steel deterioration. All pipes are subject to joint failures. Water quality deterioration includes scaling, sedimentation, and biofilm formation. Scaling is the formation of hard deposits on the interior wall of pipes. This can be a by-product of pipe corrosion combined with calcium in the water, which is called tuberculation. Sedimentation is when solids settle within the pipes, usually at recesses between scaling build-ups. When there is a change in the velocity of water flow (such as sudden use of a fire hydrant), the settled solids will be stirred up, causing water to be discolored. Biofilms can develop in highly scaled and thus rough-surfaced pipes where bacteria are allowed to grow, as the higher the roughness of the interior wall, the harder it is for disinfectant to kill the bacteria on the surface of the pipe wall. Hydraulic deterioration that affects pressures and flows can be a result of other deterioration that obstructs the water flow.
When it is time for water main renewal, there are many considerations in choosing the method of renewal. This can be open-trench replacement or one of the pipeline rehabilitation methods. A few pipeline rehabilitation methods are pipe bursting, sliplining, and pipe lining.
When an in-situ rehabilitation method is used, one benefit is the lower cost, as there is no need to excavate along the entire water main pipeline. Only small pits are excavated to access the existing water main. The unavailability of the water main during the rehabilitation, however, requires building a temporary water bypass system to serve as the water main in the affected area. A temporary water bypass system (known as temporary bypass piping) should be carefully designed to ensure an adequate water supply to the customers in the project area. Water is taken from a feed hydrant into a temporary pipe. When the pipe crosses a driveway or a road, a cover or a cold patch should be put in place to allow cars to cross the temporary pipe. Temporary service connections to homes can be made to the temporary pipe. Among many ways to make a temporary connection, a common one is to connect the temporary service connection to a garden hose. The temporary pipe should also add temporary fire hydrants for fire protection.
As water main work can disturb lead service lines, which can result in elevated lead levels in drinking water, it is recommended that when a water utility plans a water main renewal project, it should work with property owners to replace lead service lines as part of the project. | 1 | Applied and Interdisciplinary Chemistry |
On April 17, 2005, the Millstone Nuclear Power Plant in Connecticut was shut down due to a "false alarm" that indicated an unsafe pressure drop in the reactor's steam system when the steam pressure was actually nominal. The false alarm was caused by a tin whisker that short circuited the logic board responsible for monitoring the steam pressure lines in the power plant. | 1 | Applied and Interdisciplinary Chemistry |
Two papers describe MgtE, a fourth Mg uptake protein in bacteria unrelated to MgtA/B or CorA. This gene has been sequenced and the protein, 312 amino acids in size, is predicted to contain either four or five TM spanning domains that are closely arranged in the C-terminal part of the protein (see figure). This region of the protein has been identified in the Pfam database as a conserved protein domain (PF01769) and species containing proteins that have this protein domain are roughly equally distributed throughout the Eubacteria and Archaea, although it is quite rare in comparison with the distribution of CorA. However, the diversity of the proteins containing the domain is significantly larger than that of the CorA domain. The Pfam database lists seven distinct groups of MgtE domain containing proteins, of which six contain an archaic or eubacterial member. The expression of MgtE is frequently controlled by a conserved RNA structure, YkoK leader or M-box.
The figure (right), adapted from Smith et al. (1995) and the PFAM database entry, shows the computer-predicted membrane topology of the MgtE protein in Bacillus firmus OF4. The TM domains are shown in light blue. The CBS domains, named for the protein they were identified in, cystathionine-beta synthase, shown in orange, are identified in the Pfam database as regulatory domains, but the mechanism of action has not yet been described. They are found in several voltage-gated chloride channels. The orientation in the membrane and the positions of the N- and C-termini are indicated. This figure is not drawn to scale. This transporter has recently had its structure solved by x-ray crystallography.
The MgtE gene was first identified by Smith et al. (1995) during a screen for CorA-like proteins in bacteria and complements the Mg-uptake-deficient S. typhimurium strain MM281 (corA mgtA mgtB), restoring wild type growth on standard media. The kinetics of Mg transport for the protein were not determined, as Mg was unavailable. As a substitute, the uptake of Co was measured and was shown to have a km of 82 μM and a Vmax of 354 pmol min 10 cells. Mg was a competitive inhibitor with a Ki of 50 μM—the Ki of Mg inhibition of Co uptake via CorA is 10 μM. A comparison of the available kinetic data for MgtA and CorA is shown in the table. Clearly, MgtE does not transport Co to the same degree as CorA, and the inhibition of transport by Mg is also less efficient, which suggests that the affinity of MgtE for Mg is lower than that of CorA. The strongest inhibitor of Co uptake was Zn, with a Ki of 20 μM. The transport of Zn by this protein may be as important as that of Mg.
The table shows a comparison of the transport kinetics of MgtE and CorA, and key kinetic parameter values for them are listed. As shown, the data has been generated at differing incubation temperatures. km and Ki are not significantly altered by the differing incubation temperature. Conversely, Vmax shows a strong positive correlation with temperature, hence the value of Co Vmax for MgtE is not directly comparable with the values for CorA. | 1 | Applied and Interdisciplinary Chemistry |
For aircraft the US Federal Aviation Regulations suggest RHT principles, both in the air and on water, and in aircraft with side-by-side cockpit seating, the pilot-in-command (or more senior flight officer) traditionally occupies the left seat. However, helicopter practice tends to favour the right hand seat for the pilot-in-command, particularly when flying solo. | 0 | Theoretical and Fundamental Chemistry |
It has been proposed that ThTP has a specific role in nerve excitability, but this has never been confirmed and recent results suggest that ThTP probably plays a role in cell energy metabolism. Low or absent levels of thiamine triphosphate have been found in Leighs disease.
In E. coli, ThTP is accumulated in the presence of glucose during amino acid starvation. On the other hand, suppression of the carbon source leads to the accumulation, of adenosine thiamine triphosphate (AThTP). | 1 | Applied and Interdisciplinary Chemistry |
Muscular activity requires ATP, which is provided by the breakdown of glycogen in the skeletal muscles. The breakdown of glycogen, known as glycogenolysis, releases glucose in the form of glucose 1-phosphate (G1P). The G1P is converted to G6P by phosphoglucomutase. G6P is readily fed into glycolysis, (or can go into the pentose phosphate pathway if G6P concentration is high) a process that provides ATP to the muscle cells as an energy source. During muscular activity, the store of ATP needs to be constantly replenished. When the supply of oxygen is sufficient, this energy comes from feeding pyruvate, one product of glycolysis, into the citric acid cycle, which ultimately generates ATP through oxygen-dependent oxidative phosphorylation.
When oxygen supply is insufficient, typically during intense muscular activity, energy must be released through anaerobic metabolism. Lactic acid fermentation converts pyruvate to lactate by lactate dehydrogenase. Most importantly, fermentation regenerates NAD, maintaining its concentration so additional glycolysis reactions can occur. The fermentation step oxidizes the NADH produced by glycolysis back to NAD, transferring two electrons from NADH to reduce pyruvate into lactate. (Refer to the main articles on glycolysis and fermentation for the details.)
Instead of accumulating inside the muscle cells, lactate produced by anaerobic fermentation is taken up by the liver. This initiates the other half of the Cori cycle. In the liver, gluconeogenesis occurs. From an intuitive perspective, gluconeogenesis reverses both glycolysis and fermentation by converting lactate first into pyruvate, and finally back to glucose. The glucose is then supplied to the muscles through the bloodstream; it is ready to be fed into further glycolysis reactions. If muscle activity has stopped, the glucose is used to replenish the supplies of glycogen through glycogenesis.
Overall, the glycolysis steps of the cycle produce 2 ATP molecules at a cost of 6 ATP molecules consumed in the gluconeogenesis steps. Each iteration of the cycle must be maintained by a net consumption of 4 ATP molecules. As a result, the cycle cannot be sustained indefinitely. The intensive consumption of ATP molecules in the Cori cycle shifts the metabolic burden from the muscles to the liver. | 1 | Applied and Interdisciplinary Chemistry |
Machine learning algorithms have been widely used in virtual screening approaches. Supervised learning techniques use a training and test datasets composed of known active and known inactive compounds. Different ML algorithms have been applied with success in virtual screening strategies, such as recursive partitioning, support vector machines, k-nearest neighbors and neural networks. These models find the probability that a compound is active and then ranking each compound based on its probability. | 1 | Applied and Interdisciplinary Chemistry |
There are detailed descriptions of the interfacial DL in many books on colloid and interface science and microscale fluid transport. There is also a recent IUPAC technical report on the subject of interfacial double layer and related electrokinetic phenomena.
As stated by Lyklema, "...the reason for the formation of a "relaxed" ("equilibrium") double layer is the non-electric affinity of charge-determining ions for a surface..." This process leads to the buildup of an electric surface charge, expressed usually in C/m. This surface charge creates an electrostatic field that then affects the ions in the bulk of the liquid. This electrostatic field, in combination with the thermal motion of the ions, creates a counter charge, and thus screens the electric surface charge. The net electric charge in this screening diffuse layer is equal in magnitude to the net surface charge, but has the opposite polarity. As a result, the complete structure is electrically neutral.
The diffuse layer, or at least part of it, can move under the influence of tangential stress. There is a conventionally introduced slipping plane that separates mobile fluid from fluid that remains attached to the surface. Electric potential at this plane is called electrokinetic potential or zeta potential (also denoted as ζ-potential).
The electric potential on the external boundary of the Stern layer versus the bulk electrolyte is referred to as Stern potential. Electric potential difference between the fluid bulk and the surface is called the electric surface potential.
Usually zeta potential is used for estimating the degree of DL charge. A characteristic value of this electric potential in the DL is 25 mV with a maximum value around 100 mV (up to several volts on electrodes). The chemical composition of the sample at which the ζ-potential is 0 is called the point of zero charge or the iso-electric point. It is usually determined by the solution pH value, since protons and hydroxyl ions are the charge-determining ions for most surfaces.
Zeta potential can be measured using electrophoresis, electroacoustic phenomena, streaming potential, and electroosmotic flow.
The characteristic thickness of the DL is the Debye length, κ. It is reciprocally proportional to the square root of the ion concentration C. In aqueous solutions it is typically on the scale of a few nanometers and the thickness decreases with increasing concentration of the electrolyte.
The electric field strength inside the DL can be anywhere from zero to over 10 V/m. These steep electric potential gradients are the reason for the importance of the DLs.
The theory for a flat surface and a symmetrical electrolyte is usually referred to as the Gouy-Chapman theory. It yields a simple relationship between electric charge in the diffuse layer σ and the Stern potential Ψ:
There is no general analytical solution for mixed electrolytes, curved surfaces or even spherical particles. There is an asymptotic solution for spherical particles with low charged DLs. In the case when electric potential over DL is less than 25 mV, the so-called Debye-Huckel approximation holds. It yields the following expression for electric potential Ψ in the spherical DL as a function of the distance r from the particle center:
There are several asymptotic models which play important roles in theoretical developments associated with the interfacial DL.
The first one is "thin DL". This model assumes that DL is much thinner than the colloidal particle or capillary radius. This restricts the value of the Debye length and particle radius as following:
This model offers tremendous simplifications for many subsequent applications. Theory of electrophoresis is just one example. The theory of electroacoustic phenomena is another example.
The thin DL model is valid for most aqueous systems because the Debye length is only a few nanometers in such cases. It breaks down only for nano-colloids in solution with ionic strengths close to water.
The opposing "thick DL" model assumes that the Debye length is larger than particle radius:
This model can be useful for some nano-colloids and non-polar fluids, where the Debye length is much larger.
The last model introduces "overlapped DLs". This is important in concentrated dispersions and emulsions when distances between particles become comparable with the Debye length. | 0 | Theoretical and Fundamental Chemistry |
Perfluoro(2-methyl-3-pentanone) is a fluorinated ketone with the structural formula CFCFC(=O)CF(CF), a fully-fluorinated analog of ethyl isopropyl ketone. It is used as an electronics coolant liquid and fire protection fluid sold commercially by 3M under brand names such as Novec 1230, Novec 649, and FK-5-1-12. It is also known as “waterless water” or “dry water”. | 1 | Applied and Interdisciplinary Chemistry |
ISO 22197-1:2007 specifies a test method for the measurement of removal for materials that contain a photocatalyst or have superficial photocatalytic films.
Specific FTIR systems are used to characterize photocatalytic activity or passivity, especially with respect to volatile organic compounds, and representative binder matrices.
Mass spectrometry allows measurement of photocatalytic activity by tracking the decomposition of gaseous pollutants such as nitrogen NOx or | 0 | Theoretical and Fundamental Chemistry |
β-Hydroxy β-methylbutyric acid (HMB), otherwise known as its conjugate base, , is a naturally produced substance in humans that is used as a dietary supplement and as an ingredient in certain medical foods that are intended to promote wound healing and provide nutritional support for people with muscle wasting due to cancer or HIV/AIDS. In healthy adults, supplementation with HMB has been shown to increase exercise-induced gains in muscle size, muscle strength, and lean body mass, reduce skeletal muscle damage from exercise, improve aerobic exercise performance, and expedite recovery from exercise. Medical reviews and meta-analyses indicate that HMB supplementation also helps to preserve or increase lean body mass and muscle strength in individuals experiencing age-related muscle loss. HMB produces these effects in part by stimulating the production of proteins and inhibiting the breakdown of proteins in muscle tissue. No adverse effects from long-term use as a dietary supplement in adults have been found.
HMB is sold as a dietary supplement at a cost of about per month when taking 3 grams per day. HMB is also contained in several nutritional products, including certain formulations of Ensure and Juven. HMB is also present in insignificant quantities in certain foods, such as alfalfa, asparagus, avocados, cauliflower, grapefruit, and catfish.
The effects of HMB on human skeletal muscle were first discovered by Steven L. Nissen at Iowa State University in the . HMB has not been banned by the National Collegiate Athletic Association, World Anti-Doping Agency, or any other prominent national or international athletic organization. In 2006, only about 2% of college student athletes in the United States used HMB as a dietary supplement. As of 2017, HMB has found widespread use as an ergogenic supplement among young athletes. | 1 | Applied and Interdisciplinary Chemistry |
The equilibrium temperature is neither an upper nor lower bound on actual temperatures on a planet. There are several reasons why measured temperatures deviate from predicted equilibrium temperatures. | 0 | Theoretical and Fundamental Chemistry |
The ten-step catabolic pathway of glycolysis is the initial phase of free-energy release in the breakdown of glucose and can be split into two phases, the preparatory phase and payoff phase. ADP and phosphate are needed as precursors to synthesize ATP in the payoff reactions of the TCA cycle and oxidative phosphorylation mechanism. During the payoff phase of glycolysis, the enzymes phosphoglycerate kinase and pyruvate kinase facilitate the addition of a phosphate group to ADP by way of substrate-level phosphorylation. | 1 | Applied and Interdisciplinary Chemistry |
"European Parliament and Council Directive 94/36/EC of 30 June 1994 on colours for use in foodstuffs" harmonized rules and approved Sunset Yellow FCF for use in foodstuffs in the whole of the European Union. Before that time, approved amounts was up to each country, but naming and composition was standardized.
Sunset yellow FCF was not approved in Norway before 2001. That was the time when the 94/36/EC directive of 1994 was included in EFTA (now EEC) rules and came into effect, after years of delaying tactics from the Norwegian side and a heated political debate.
In 2008, the Food Standards Agency of the UK called for food manufacturers to voluntarily stop using six food additive colours, tartrazine, allura red, ponceau 4R, quinoline yellow WS, sunset yellow and carmoisine (dubbed the "Southampton 6") by 2009, and provided a document to assist in replacing the colors with other colors.
An EU regulation came into effect in 2010 mandating that food manufacturers include a label on foods containing the Southampton 6 stating: "may have an adverse effect on activity and attention in children". | 0 | Theoretical and Fundamental Chemistry |
In whole animal-based approaches, phenotypic screening is best exemplified where a substance is evaluated for potential therapeutic benefit across many different types of animal models representing different disease states. Phenotypic screening in animal-based systems utilize model organisms to evaluate the effects of a test agent in fully assembled biological systems. Example organisms used for high-content screening include the fruit fly (Drosophila melanogaster), zebrafish (Danio rerio) and mice (Mus musculus). In some instances the term phenotypic screening is used to include the serendipitous findings that occur in clinical trial settings particularly when new and unanticipated therapeutic effects of a therapeutic candidate are uncovered.
Screening in model organism offers the advantage of interrogating test agents, or alterations in targets of interest, in the context of fully integrated, assembled, biological systems, providing insights that could otherwise not be obtained in cellular systems. Some have argued that cellular based systems are unable to adequately model human disease processes that involve many different cell types across many different organ systems and that this type of complexity can only be emulated in model organisms. The productivity of drug discovery by phenotypic screening in organisms, including serendipitous findings in the clinic, are consistent with this notion. | 1 | Applied and Interdisciplinary Chemistry |
In colloidal chemistry, an aggregation number is a description of the number of molecules present in a micelle once the critical micelle concentration (CMC) has been reached. In more detail, it has been defined as the average number of surfactant monomers in a spherical micelle.
The aggregation number of micelles can be determined by isothermal titration calorimetry when the aggregation number is not too high.
Another classical experiment to determine the mean aggregation number would involve the use of a luminescent probe, a quencher and a known concentration of surfactant. If the concentration of the quencher is varied, and the CMC of the surfactant known, the mean aggregation number can be calculated. | 0 | Theoretical and Fundamental Chemistry |
The aquatic inorganic carbon system is composed of the various ionic, dissolved, solid, and/or gaseous forms of carbon dioxide in water. These species include dissolved carbon dioxide, carbonic acid, bicarbonate anion, carbonate anion, calcium carbonate, magnesium carbonate, and others. The relative amounts of each species in a body of water depends on physical variables including temperature and salinity, as well as chemical variables like pH and gas partial pressure. Variables like alkalinity and dissolved (or total) inorganic carbon further define a mass and charge balance that constrains the total state of the system.
Given any two of the four central inorganic carbon system parameters (pH, alkalinity, dissolved inorganic carbon, partial pressure of carbon dioxide) the remainder may be derived by solving a system of equations that adhere to the principles of chemical thermodynamics.
For most of the 20th century, chemical equilibria in marine and freshwater systems was calculated according to various conventions, which led to discrepancies among laboratories' calculations and limited scientific reproducibility. Since 1998, a family of software programs called CO2SYS has been widely used. This software calculate chemical equilibria for aquatic inorganic carbon species and parameters. Their core function is to use any two of the four central inorganic carbon system parameters (pH, alkalinity, dissolved inorganic carbon, and partial pressure of carbon dioxide) to calculate various chemical properties of the system. The programs are widely used by oceanographers and limnologists to understand and predict chemical equilibria in natural waters. | 0 | Theoretical and Fundamental Chemistry |
Corrosion mapping by ultrasonics is a nonintrusive (noninvasive) technique which maps material thickness using ultrasonic techniques.
Variations in material thickness due to corrosion can be identified and graphically portrayed as an image.
The technique is widely used in the oil and gas industries for the in-service detection and characterization of corrosion in pipes and vessels.
The data is stored on a computer and may be color coded to show differences in thickness readings.
Corrosion may be mapped using Zero degree ultrasonic probes, an Eddy current array and/or Time of flight detection methods.
The book Nondestructive Examination of Underwater Welded Structures by Victor S. Davey describes a "fully automated dual axis robotic scanner used for corrosion mapping normally using a single zero degree compression probe scanned in a raster pattern over the area of interest."
He also goes on to explain that "typically a 4 mm by 4 mm raster" is used. | 1 | Applied and Interdisciplinary Chemistry |
Soap bubble performances combine entertainment with artistic achievement. They require a high degree of skill. Some performers use common commercially available bubble liquids while others compose their own solutions. Some artists create giant bubbles or tubes, often enveloping objects or even humans. Others manage to create bubbles forming cubes, tetrahedra and other shapes and forms. Bubbles are sometimes handled with bare hands. To add to the visual experience, they are sometimes filled with smoke, vapour or helium and combined with laser lights or fire. Soap bubbles can be filled with a flammable gas such as natural gas and then ignited.
Professional bubble artists include Tom Noddy, Fan Yang and The Amazing Bubble Man. | 1 | Applied and Interdisciplinary Chemistry |
The first electron crystallographic protein structure to achieve atomic resolution was bacteriorhodopsin, determined by Richard Henderson and coworkers at the Medical Research Council Laboratory of Molecular Biology in 1990. However, already in 1975 Unwin and Henderson had determined the first membrane protein structure at intermediate resolution (7 Ångström), showing for the first time the internal structure of a membrane protein, with its alpha-helices standing perpendicular to the plane of the membrane. Since then, several other high-resolution structures have been determined by electron crystallography, including the light-harvesting complex, the nicotinic acetylcholine receptor, and the bacterial flagellum. The highest resolution protein structure solved by electron crystallography of 2D crystals is that of the water channel aquaporin-0. In 2012, Jan Pieter Abrahams and coworkers extended electron crystallography to 3D protein nanocrystals by rotation electron diffraction (RED). | 0 | Theoretical and Fundamental Chemistry |
Amorphous silicon (a-Si) is a popular solar cell material owing to its low cost and ease of production. Owing to disordered structure (Urbach tail), its absorption extends to the energies below the band gap resulting in a wide-range spectral response; however, it has a relatively low solar cell efficiency. Protocrystalline Si (pc-Si:H) also has a relatively low absorption near the band gap, owing to its more ordered crystalline structure. Thus, protocrystalline and amorphous silicon can be combined in a tandem solar cell, where the top thin layer of a-Si:H absorbs short-wavelength light whereas the longer wavelengths are absorbed by the underlying protocrystalline silicon layer. | 0 | Theoretical and Fundamental Chemistry |
The value is important because it helps determine the Stoichiometry of a system for example in polyurethanes. The value may also be used to calculate equivalent weight and if the functionality is known, the molecular weight also. | 0 | Theoretical and Fundamental Chemistry |
The cyclic relation is also known as the cyclic rule or the Triple product rule. Setting the second term in brackets equal to zero yields
Using a reciprocity relation for on this equation and reordering gives a cyclic relation (the triple product rule),
If, instead, reciprocity relations for and are used with subsequent rearrangement, a standard form for implicit differentiation is obtained: | 0 | Theoretical and Fundamental Chemistry |
Sodium peroxide is added to the compound to oxidise phosphorus to sodium phosphate. It is boiled with concentrated HNO and then ammonium molybdate is added. A yellow precipitate (ammonium phosphomolybdate) indicates the presence of phosphorus.
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"Clinker" is from Dutch, and was originally used in English to describe clinker bricks. The term was later applied to hard residue, due to its similar appearance. | 1 | Applied and Interdisciplinary Chemistry |
Nascent hydrogen is an outdated concept in organic chemistry that was once invoked to explain dissolving-metal reactions, such as the Clemmensen reduction and the Bouveault–Blanc reduction. Since organic compounds do not react with H, a special state of hydrogen was postulated. It is now understood that dissolving-metal reactions occur at the metal surface, and the concept of nascent hydrogen has been discredited in organic chemistry. However, the formation of atomic hydrogen is largely invoked in inorganic chemistry and corrosion sciences to explain hydrogen embrittlement in metals exposed to electrolysis and anaerobic corrosion (e.g., dissolution of zinc in strong acids (HCl) and aluminium in strong bases (NaOH). The mechanism of hydrogen embrittlement was first proposed by Johnson (1875). The inability of hydrogen atoms to react with organic reagents in organic solvents does not exclude the transient formation of hydrogen atoms capable to immediately diffuse into the crystal lattice of common metals (steel, titanium) different from these of the platinoid group (Pt, Pd, Rh, Ru, Ni) which are well known to dissociate molecular dihydrogen (H) into atomic hydrogen. | 0 | Theoretical and Fundamental Chemistry |
An energy carrier is a substance (fuel) or sometimes a phenomenon (energy system) that contains energy that can be later converted to other forms such as mechanical work or heat or to operate chemical or physical processes.
Such carriers include springs, electrical batteries, capacitors, pressurized air, dammed water, hydrogen, petroleum, coal, wood, and natural gas. An energy carrier does not produce energy; it simply contains energy imbued by another system. | 0 | Theoretical and Fundamental Chemistry |
A good example of convective instability can be found in our own atmosphere. If dry mid-level air is drawn over very warm, moist air in the lower troposphere, a hydrolapse (an area of rapidly decreasing dew point temperatures with height) results in the region where the moist boundary layer and mid-level air meet. As daytime heating increases mixing within the moist boundary layer, some of the moist air will begin to interact with the dry mid-level air above it. Owing to thermodynamic processes, as the dry mid-level air is slowly saturated its temperature begins to drop, increasing the adiabatic lapse rate. Under certain conditions, the lapse rate can increase significantly in a short amount of time, resulting in convection. High convective instability can lead to severe thunderstorms and tornadoes as moist air which is trapped in the boundary layer eventually becomes highly negatively buoyant relative to the adiabatic lapse rate and escapes as a rapidly rising bubble of humid air triggering the development of a cumulus or cumulonimbus cloud. | 1 | Applied and Interdisciplinary Chemistry |
Termination of elongation depends on eukaryotic release factors. The process is similar to that of bacterial termination, but unlike bacterial termination, there is a universal release factor, eRF1, that recognizes all three stop codons. Upon termination, the ribosome is disassembled and the completed polypeptide is released. eRF3 is a ribosome-dependent GTPase that helps eRF1 release the completed polypeptide. The human genome encodes a few genes whose mRNA stop codon are surprisingly leaky: In these genes, termination of translation is inefficient due to special RNA bases in the vicinity of the stop codon. Leaky termination in these genes leads to translational readthrough of up to 10% of the stop codons of these genes. Some of these genes encode functional protein domains in their readthrough extension so that new protein isoforms can arise. This process has been termed functional translational readthrough. | 1 | Applied and Interdisciplinary Chemistry |
Plasmas find applications in many fields of research, technology and industry, for example, in industrial and extractive metallurgy, surface treatments such as plasma spraying (coating), etching in microelectronics, metal cutting and welding; as well as in everyday vehicle exhaust cleanup and fluorescent/luminescent lamps, fuel ignition, and even in supersonic combustion engines for aerospace engineering. | 0 | Theoretical and Fundamental Chemistry |
The molecular weight, bioavailability, protein binding, elimination half-life, the time to achieve maximum plasma concentration and binding affinity are present in the table below.
* t: Biological half-life
* t: Time to achieve maximum plasma concentration
* pK: the measurement of ligand binding affinity
Methylnaltrexone bromide has poor oral bioavailability, and for that reason, every other day it is administered subcutaneously. About half of the dose is excreted in the urine and somewhat less in feces with 85% eliminated unchanged.
Alvimopan has considerable low bioavailability (6%) due to its high binding affinity and low dissociation rate. Essentially, alvimopan is mediated by biliary secretion with an average plasma clearance of 400 ml/min. Metabolism of alvimopan is via intestinal flora resulting in hydrolysis of alvimopan to the active amide metabolite (ADL 08-0011). However, the metabolite is considered clinically irrelevant due to its low binding affinity.
When naloxegol is given with a fatty meal, absorption increases. Clearance is mostly via hepatic metabolism (P450-CYP3A) with unknown actions of the metabolites. Naloxegol has small fragments eliminated by renal excretion.
Naldemedine metabolites mainly via CYP3A to nor-naldemedine, it also metabolites via UDP-glucuronosyltransferase 1A3 to naldemedine 3-G, but in a lesser extent. Those metabolites are both opioid receptor antagonists but are less potent than the parent compound. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits